1. Field of the Invention
This invention relates to an anchor box embedded in concrete and for retaining an anchor nut in concrete.
2. Description of the Prior Art
In the case of constructing concrete structures such, for example, as a quay wall in harbor facilities, it has been the common practice to embed beforehand an anchor bolt in the quay wall concrete for the purpose of fitting a marine fender or the like to the front surface of the quay wall.
Such an anchor bolt is provided at its one end with a threaded portion and at its opposite end with a proper rotation preventive means. The anchor bolt is embedded in concrete with the threaded end exposed out of the concrete and after the concrete structure has been hardened, the exposed threaded end is engaged with a nut. However, when the nut is fastened to a proper position, it is inevitable that the threaded end portion of the anchor bolt protrudes from the nut. As a result, such anchor bolt enbedded in concrete is unsuitable for fitting a marine fender to the quay wall.
That is, the anchor bolt embedded in concrete has the disadvantages that the exposed threaded portion thereof is corroded by splashes of sea water or the like, that the protruded surplus threaded portion causes the effective stroke of deformation of the marine fender to make small, and there is a risk that hulls of ships will be damaged.
In order to effectively overcome the above mentioned drawback, an anchor nut may be embedded in the concrete structure. But, in this case, it is difficult to determine the position of the anchor nut during concrete placing work. In addition, there is a risk of tapped holes being clogged with concrete. Moreover, a fastening bolt insertion hole tends to be easily misaligned with the anchor nut.
In order to overcome such disadvantage, if the anchor nut is combined beforehand with the fastening bolt or an auxiliary bolt and eventually with a stay pipe for the purpose of determining the position of the anchor nut with respect to a concrete placing molding frame, there is a risk of the bolt or the like, which is to be taken out of the concrete after the concrete has been hardened, being firmly secured to the concrete, thereby rendering the workability extremely difficult.